/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.giraph.aggregators;

import org.apache.hadoop.io.DoubleWritable;

/**
 * Aggregator that stores a value that is overwritten once another value is
 * aggregated. This aggregator is useful for one-to-many communication from
 * master.compute() or from a special vertex. In case multiple vertices write
 * to this aggregator, its behavior is non-deterministic.
 */
public class DoubleOverwriteAggregator extends
    BasicAggregator<DoubleWritable> {
  @Override
  public void aggregate(DoubleWritable value) {
    getAggregatedValue().set(value.get());
  }

  @Override
  public DoubleWritable createInitialValue() {
    return new DoubleWritable(0);
  }
}
